Wim Hof can remain in ice-cold water for nearly two hours without significant changes in body temperature due to his thermal sensors heating up and burning brown fat, which also leads to the conversion of white fat into brown fat.

“And Wim Hof is able to sit for two hours, or 1 hour and 58 minutes, or something like that, to be precise, in ice-cold water without is a significant change in body temperature. Why? Because his thermal sensor is heating up and burning the brown fat, "Come on, boys," and afterwards, you're going change the white fat into brown fat, which is…the brown feathers in this area of your body and so you regenerate that.”